Project Summary Autism Spectrum Disorder (ASD) is defined by core deficits in social communication and interaction, as well as repetitive patterns of behavior and/or interests. In addition, the presence of atypical sensory and multisensory processing is reported to be characteristic of a majority of those suffering from ASD and has recently been included as a diagnostic feature in the DSM-5. The deficit in integrating information across the different senses is postulated to scaffold the higher-order social and cognitive deficits present in ASD. Recent work from our group has demonstrated that individuals with ASD possess abnormally larger multisensory temporal binding windows; that is, they integrate sensory information over larger temporal disparities than their typically developing (TD) peers do. In contrast to the emphasis on temporal processing, a second major physical feature ruling multisensory integration ? space ? has been understudied in ASD. This is surprising as space is a core element of any social interaction. Within the scope of the current project, we seek to delineate spatial, temporal, and spatio-temporal binding windows throughout three-dimensional space, as well as to examine for the first time the neural correlates of spatio-temporal binding via electroencephalography (EEG). Based on our previous findings in TD adults, we hypothesize that temporal binding windows will be larger within peri- personal space, the space immediately adjacent to and surrounding your body. In contrast, we expect that spatial binding windows will be larger at farther distances from the body (due to poorer visual and auditory acuity). As as corollary to this, we predict that spatio-temporal binding windows will remain of similar size across space, as the components of these sensory filters are changing in opposite directions across the proximal to distal (i.e., distance) axis. Further, we expect the gradient from peri- to extra-personal space dictating emphasis on either temporal or spatial aspect of multisensory stimuli to be steeper for individuals with ASD than TD. From an electrical neuroimaging standpoint, we hypothesize that gamma (30-50Hz) activity will provide a powerful proxy measure of sensory binding, and thus to reflect whether spatial or temporal features are most strongly influencing multisensory spatio-temporal binding. We expect that activity in regions of parietal cortex (i.e., the where pathway) will be more strongly reflective of spatial binding, which will be over- emphasized in ASD in the far space, whereas gamma activity in temporal cortex (i.e., the when/what pathway) will be more reflective of temporal binding, which will be emphasized in ASD in the close space. In carrying out the proposed project, we expect to gain a better understanding into how ASD individuals build a sensory representation of the world differently from the healthy brain, and in doing so, to provide important clues as to how to best communicate and interact with these individuals.